The present invention relates to a switch device having a rubber sheet which is elastically deformed by receiving an operating force.
Usually, as a switch device used in a vehicle, for instance, a switch device is known that includes a base board having a fixed contact on one surface and a rubber sheet formed with an elastic material to cover the surface of the fixed contact side of the base board. The rubber sheet has a contact dome part that covers the fixed contact on the base board. A movable contact is provided in the base board side of the contact dome part. In this case, the contact dome part of the rubber sheet forms a contact chamber as a hollow space between the base board and the contact dome part. The contact chamber is allowed to communicate with an air accumulating chamber whose volume is larger than that of the contact chamber.
In the switch device having such a structure, when an operating force is applied to the contact dome part of the rubber sheet, the contact dome part is elastically deformed. Thus, the movable contact provided in the contact dome part comes into contact with the fixed contact provided on the base board. At this time, air in the contact chamber is compressed by the contact dome part of the rubber sheet to be pushed out to the air accumulating chamber. Then, when the operating force is released, the contact dome part in the rubber sheet is restored so that the movable contact of the contact dome part is disengaged from the fixed contact on the base board. Thus, the air pushed out to the air accumulating chamber is sucked to the contact chamber. As described above, during an operation of the switch device, the air in the contact chamber enters the air accumulating chamber and the air exits from the air accumulating chamber, what is called, the switch device breathes. Thus, a reaction of the air due to the compression of the air during the operation is prevented to make the operation easy.
However, in the above-described structure, the air accumulating chamber needs to ensure the volume larger than that of the contact chamber. Accordingly, the air accumulating chamber is frequently provided over a part on which, for instance a terminal of a connector or electronic parts are mounted on the base board. In this case, there is a fear that the contact chamber may possibly suck foreign materials such as solder chips remaining in the air accumulating chamber by breathing. Thus, the foreign materials are occasionally sandwiched between the fixed contact and the movable contact to cause an imperfect contact of these contacts.
Under the above-described circumstance, a structure is disclosed that a foreign material accumulating chamber is provided between a contact chamber and an air accumulating chamber (for instance, patent literature 1). In such a structure, the contact chamber does not directly communicate with the air accumulating chamber. Accordingly, when the contact chamber breathes by an operation, foreign materials present in the air accumulating chamber are temporarily sucked to the foreign material accumulating chamber. Thus, the foreign materials present in the air accumulating chamber are prevented from directly entering the contact chamber.    [Patent Literature 1] JP-A-2010-40490
However, the foreign material accumulating chamber directly communicates with the contact chamber. Accordingly, there is a fear that the contact chamber may possibly suck the foreign materials temporarily collected to the foreign material accumulating chamber.